Doctoral defence in Mechanical Engineering - Gifty Oppong
The Aula
Ph.D. student: Gifty Oppong
Dissertation title: Tribological Properties and Corrosion Behavior of Coatings for Geothermal Applications
Opponents:
Dr. Ralph Bässler, Group Leader, Department of Safety of Structures Bundesanstalt für Materialforschung und -prüfung (BAM), Germany
Dr. Roy Johnsen, Professor at the Norwegian University of Science and Technology (NTNU), Trondheim
Advisor: Dr. Sigrun Nanna Karlsdottir, professor at the the Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, University of Iceland
Also in the doctoral committee
Dr. Danyil Kovalov, Research Scientist at Alsym Energy, USA
Dr. Andri Stefánsson, professor and Head of the Faculty of Earth Sciences at the University of Iceland
Chair of Ceremony: Dr. Rúnar Unnþórsson, Professor and Head of the Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, University of Iceland
Abstract:
The increasing global demand for renewable energy has resulted in the increased exploration of geothermal energy resources, which presents corrosion and wear challenges. The objective of the PhD project is to investigate the friction, wear and corrosion behavior of available and novel coatings designed to add wear and corrosion resistance to steels currently used in geothermal applications. The coatings include tungsten carbide (WC) cermet-, nickel alloy based-, amorphous iron based-, graphene oxide based-, electroless nickel-phosphorus duplex-, and high entropy alloy (HEA) based- coatings. The results demonstrated that the coatings’ hardness influenced abrasion and wear resistance, but the surface roughness complicated friction and sliding behavior. Further autoclave testing revealed that, the wear-resistant coatings acted as a physical barrier in the test solution, preventing steel corrosion. However, deviations were dependent on the coating microstructure, physical properties, and the chemistry of the test environment, promoting localized corrosion effects. In the 120 °C water test, all the coatings were protective by resisting substrate corrosion. After liquid/vapor phase exposure in the challenging environment (i.e., 250 °C with H2S/CO2), the coatings were subjected to either internal attack, surface deposits or substrate corrosion. This work revealed good corrosion resistance of the wear resistant HVOF developed HEA in all test environments and thus encouraging industrial exploitation of the coating in CO2/H2S-containing fluid commonly encountered in geothermal fields. The findings established systems that produce suitable corrosion- and wear- resistant coatings for targeted applications that can be incorporated into early project phases in geothermal energy exploration.
About the doctoral candidate
Gifty Oppong was born and raised in Ghana where she graduated with a Bachelors in Materials engineering in the University of Science and Technology.
She was awarded with Erasmus EU scholarship to study a Joint Masters programme in Surface Engineering at the universities of Leeds, Ljubljan, Lulea and Coimbra. Gifty started her doctoral studies at the University of Iceland in 2018.
Gifty Oppong
